You can see a little bit of the subtending sporophyll, which looks very thin and narrow at this level of section. There is an extra little envelope on the top of the sporangium called a velum. When you look at the contents of the sporangium you can see little fingers of sterile tissue extending from either side of the sporangium. These are called trabeculae, and increase the surface area of tissues that can provide nutrition to the developing spores. 

In the photo on the right you can see details of the Isoetes microspores. Note that they are somewhat elongate and have a single line (monolete mark) rather than a three-armed trilete mark.